The program is directed toward identifying through the use of radio-chemicals, pathways in the nervous system. For that purpose, radioactive substances are especially prepared and injected either hydraulically or electrophoretically into nerve tissue. Thereafter the preparation is allowed to survive for a period of time which has been established experimentally as sufficient to allow transport of the label to the most remote portions of the pathway under study. Through the use of autoradiography the location of the radiochemical is then established in serial sections of the tissues. In some cases semi-quantitative data on the number and position of labelled nerve elements is established through the use of automated techniques. These last named procedures include the development of both hardware and software to support our methods of analysis. The results obtained so far indicate that several neural pathways can be so examined. Data on sizes, numbers, and location in nerve tissue of the labelled elements have been obtained. BIBLIOGRAPHIC REFERENCES: Boyle, P.J.R. and D.G. Whitlock, The mini-computer as a microscope accessory, Biomed. Sci.Inst., 11:79-83, 1975. Cook, M.L. and D.G. Whitlock, Axoplasmic transport in the toad Bufo marinus, Brain Res., 96, no. 2:247-265, 1975.